"A group of heavily armed people attacked the presidential palace. They were stopped at the first roadblock. Our soldiers fought with them, arrested some of them and six people were killed."

Mende said the situation was under control and authorities were trying to identify the suspects. No further details on the casualties were immediately available.

Separately, a presidential source said President Joseph Kabila was not in the palace when the attack happened but that he had now returned there and was safe.

Kabila came to power when his father was assassinated in 2001. He faces presidential and parliamentary elections in November this year, the second such polls since the official end of the 1998-2003 war.

In a controversial January 15 move, parliament backed proposals by Kabila to reduce the presidential vote to a single round -- scrapping the possibility of a run-off between the two leading candidates if neither has an absolute majority.

The change means the winner can claim the presidency with less than 50 percent popular support and is seen boosting Kabila's chances of victory because of the fragmented state of the opposition.